Cumulative sum with group by

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Computational Science

Q&A for scientists using computers to solve scientific problems

DECLARE @t TABLE(ColumnA INT, ColumnB VARCHAR(50));

INSERT INTO @t VALUES
(2,           'a'),
(3  ,         'b'),
(4   ,        'c'),
(5    ,       'd'),
(1     ,      'a');

;WITH cte
AS
(
   SELECT ColumnB, SUM(ColumnA) asum
   FROM @t 
   gROUP BY ColumnB
  
), cteRanked AS
(
   SELECT asum, ColumnB, ROW_NUMBER() OVER(ORDER BY ColumnB) rownum
   FROM cte
) 


select * from cteRanked 
/*
select * from cteranked
to this:
SELECT (SELECT SUM(asum) FROM cteRanked c2 WHERE c2.rownum <= c1.rownum) AS ColumnA, ColumnB
FROM cteRanked c1;
ColumnA          ColumnB
3                 a
6(=3+3)           b   
10(=4+3+3)        c   
15(=5+4+3+3)      d 
*/

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